Effect of different types of mesogenic compounds with fluorine and cyano-group on the working temperature of polymer dispersed liquid crystal films.

• The liquid crystal phase temperature ranges of PDLC films are increased by using high clearing-point mesogenic compounds. • The working temperature range of the PDLC film is further expanded. • The effects of different mesogenic compound structures on the performance of PDLC films are studied. • The influence of mesogenic compound structure on the properties of the host liquid crystal is thoroughly investigated. As a type of smart dimming film, polymer dispersed liquid crystal (PDLC) film can meet the functional requirements in fields of displays and smart windows, but its narrow working temperature range is far from satisfactory for outdoor applications. To solve this problem, two types of high-clearing point mesogenic compounds with different end groups were introduced and the effects of their chemical structure on the working temperature range of PDLC film were investigated. Results show that the PDLC film doped with 10 wt% fluorine-containing LC molecule (3F) has a low driving voltage (<36 V) at −20 °C, but its contrast ratio (CR) value at the high temperature is disappointing. Furthermore, by adding 10 wt% cyano LC molecule (3 N), the film maintains an excellent CR value (62) at 90 °C. This work provides theoretical guidance and experimental support for broadening the working temperature of PDLC films, which is an important factor for their applications in automobile smart windows. [ABSTRACT FROM AUTHOR]